The currently well known technique of angioplasty presents many limitations. This technique consists in introducing an inflatable bag as far as the shrunk area of the vessel where the deposits are situated and in inflating said bag by means of fluid until pressures of about 5 atmospheres are reached. The primary object of this technique is not to remove deposits but to clear the vessels. The deformation due to the force applied by the inflated bag on the deposits can, in a large number of cases, be reversible and cause more stenoses in patients who have been treated by angioplasty.
Attempts have been made during the last few years, to remove deposits by a destructive action, more particularly with a rotary tool adapted to remove, superficially, the material constituting the deposit.
In document EP 0086048, the rotary tool comprises a body of ellipsoid shape along which extends at least one helical-shaped edge. This tool is a high speed cutting and abrasive tool which, by turning, is capable of cracking and removing the relatively hard intra-arterial deposits, without damaging the arterial walls, by repeatedly hitting said deposits with one or more of the cutting faces provided on the edge or edges.
In the device described in document EP 0086048, the rotary tool has an attacking diameter which is constant and therefore gives no possibility for adapting the destroying action as a function of the extent of the deposits, hence of the obstruction of the vessel.
A rotary atherectomy device has already been proposed in document EP 0442137, in which the rotary tool can have an adjustable configuration. Said rotary tool is composed of flexible filiform elements which are joined together by their distal and proximal ends; this device further comprises a system for bringing the two ends axially closer, such as for example a pull-in wire actuatable by the operator which makes it possible to bring the distal end of the rotary tool towards the proximal end of the flexible filiform elements. During this closing-in movement, each filiform element bends, this leading to a transversal expansion of the rotary tool.
Given that the filiform elements are, during their introduction, approximately rectilinear, the rotary tool can be introduced into the vessel with a catheter of small dimension. This is a great advantage over the tool which has a constant attacking diameter for which the introduction catheter has to have an inner diameter smaller than the diameter of the rotary tool. Nonetheless, the device described in document EP 0442137 is relatively complex in design, particularly because of the presence of the means for bringing axially closer the two proximal and distal ends of the filiform elements constituting the rotary tool. Another device of the same type is described in U.S. Pat. No. 5,030,201.